Signal processing in a novel radar system for monitoring insect migration

A vertical-looking radar (VLR) has been developed to allow routine, automatic monitoring of the migratory flight of insects. A novel feature of this radar is that its beam nutates by a fraction of a beamwidth and at the same time, the plane of (linear) polarisation is rotated. Insects flying individually through this beam produce a time-varying signal from which their horizontal speed and direction of motion, their orientation, and three radar scattering cross-section terms can be extracted. These terms are related to the insect body mass and shape. This paper outlines the principle of operation of the radar, and describes how all six of these target properties can be extracted from the radar signal, using a high-performance, PC-compatible 486 computer, programmed in Transera HTBasic. The data display and storage procedures are also described.